Boron Arsenide Just Surpassed Diamond in Heat Transfer

An international team of scientists led by University of Houston engineers just proved a long-held thermal conductivity theory incorrect. Their work pushed the boundaries of material science further and could inspire several corresponding breakthroughs in the coming months. As such, it’s seen as a major milestone in the scientific community. Here’s what you need to know.

Why Thermal Conductivity Matters in Modern Electronics

To grasp the importance of this breakthrough, it’s vital to understand the crucial role thermal barrier coating plays in today’s technology. These coatings, usually applied to metallic components, help reduce heat exposure to vital components.

The thermal conductivity barrier they create helps make today’s engines more durable, computers faster, and is an important part of many industrial sectors. As such, there’s constant research going into improving these surfaces. While there have been many advancements in synthetic materials, none could ever compete with nature.

Diamonds

For many decades, diamonds have been considered the best isotropic material for heat conduction. Isotropic materials are unique in that they offer uniform heat distribution across all crystallographic directions. Keenly, they excel at heat transfer for several key reasons, including their tight covalent carbon-carbon bonds.

Limitations of Diamond as a Thermal Conductor

Some issues come along with using diamond thermal coatings that continue to give researchers reason to further their search for other materials. For one, they are more expensive than other isotropic materials. Also, they can be difficult to work with.

Despite these limitations, diamonds are still used when rapid heat dissipation is mission-critical. However, a growing number of engineers now believe that it’s possible to exceed diamond’s performance using synthesised materials. One material that has seen increasing attention is Boron Arsenide.

Boron Arsenide (BAs)

Boron Arsenide (BAs) first emerged in 1959 after scientists successfully synthesized boron and arsenic. This early experimentation sat dormant for many decades until the 2000s. It was then that advancements in computer modeling and material science suddenly made it possible to see how BAs could serve as a potential heat conductor.

It wasn’t until 2013, when David Broido, a Boston College physicist, made a stark prediction in which he described a scenario in which BAs outperformed diamond’s thermal conductivity. He used calculations to show that the material was capable of achieving thermal conductivity of 2200 W/m·K at room temperature using a three-phonon scattering approach.

In 2015, Houston University Professor Zhifeng Ren took the concept further when he and his team grew BAs crystals in their lab and tested them. He conducted several experiments where he achieved a single crystal thermal conductivity of 1500 W/m·K at room temperature.

This rating placed BAs in a close second behind diamonds in terms of thermal conductivity. It also inspired further research into the material and ways to achieve the optimal thermal conductivity of 2200 W/m·K at room temperature predicted by Broido years prior.

Challenges in Achieving High-Purity BAs

Work has been conducted on BAs as a thermal conductor since that time. However, changes in the phonon scattering strategies and other issues led engineers to see their results reduced to about 1,300 W/mK. Thankfully, a recent study has shown what caused these limitations and how to reduce them.

Boron Arsenide Study

The Thermal conductivity of boron arsenide above 2100 W per meter per Kelvin at room temperature¹ study published in the scientific journal Materials Today, reveals how engineers were able to obtain unprecedented thermal conductivity of 2100 W/m·K in boron arsenide single crystals at room temperature.

What Was the Problem?

As engineers noted, the math checked out, but the experiments weren’t meeting the expectations. That’s when they decided to reevaluate the core components and strategy to see where improvements could be made. One key area where they noted a loss of conductivity is impurities.

Source – Materials Today

Notably, in isotropic materials, the heat transfer capabilities follow the crystallographic pathways of the material. In an optimal setting, these pathways provide smooth travel. However, engineers noted that in previous experiments, the crystals used had several imperfections that actually hindered performance.  As such, they set off to grow the purest BAs possible.

How to Grow BAs without Impurities

To accomplish this task, they started off reimagining the process from the ground up. They began with ultrapure arsenic. From there, I was put through a four-step synthesis, which reduced impurities further.

The next step was to fully scrub a quartz tube. Notably, the engineers used standard semiconductor cleaning processes involving multiple ultrasonic cleanings using several materials, including acetone, ethanol, and deionized water. Then, it was dried in an oven, eliminating any leftover moisture.

From there, the engineers used transmission lights to check thermal conductivity and for impurities. They immediately noted that they had a substantially lower point defect concentration in the individual crystals compared to past attempts.

How Researchers Measured BAs Thermal Conductivity

The scientist tested the crystals’ thermal conductivity utilizing several very accurate methods. The team first used the time-domain thermoreflectance (TDTR) method to register thermal conductivity. In this test, the engineers coated the crystals with a 100-nm Al transducer layer using electron beam evaporation to ensure accuracy.

From there, the group utilized Raman spectroscopy to discover any remaining impurities in the crystals. They then combined the data to gain an accurate overview of the materials’ capabilities and shortcomings. What they found would change thermal dynamics moving forward.

Record-Breaking Thermal Conductivity Results

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The team’s test proved that BAs were capable of achieving diamond-level thermal conductivity. Specifically, the scientists recorded 2,100 W/mK at room temperature. Notably, the Raman spectra enabled engineers to observe a T−1.8 dependence, opening the door for further research and performance improvements.

The engineers noted that a modified theoretical calculation would enable them to tune the process to utilize a three-phonon scattering for phonons in the 4–8 THz range, rather than a four-phonon scattering commonly used today. Using this approach, the team succeeded in recording temperature dependence from 300 to 400 K.

Boron Arsenide Benefits

This work brings many benefits to the market. For one, it opens the door for tomorrow’s high-tech devices to become much more accessible and affordable. Diamonds are expensive and rare, whereas BAs can be made on demand. Additionally, they’re easier to manufacture and integrate.

Boron Arsenide as a Semiconductor Material

One unexpected discovery was that BAs act as superior semiconductors. The tests revealed that the BAs they created outperformed silicon in several key categories. Specifically, they offer better conductivity, carrier mobility, thermal expansion, and can support a wider band gap.

Inspire a New Era in Thermal Material Science

This work demonstrates why scientists need to continually push the boundaries to excel in their results. For decades, diamonds sat as the undisputed kings of thermal conductivity. Now, the entire scientific community must reevaluate its theories, leading to room for new advancements that were previously considered impossible.

Boron Arsenide Real-World Applications and Timeline

There are many applications for this work. For one, the study will change the way manufacturers think about thermal management. If this material can be consistently synthesised with lower cost and more availability than diamond alternatives, it opens the door for next-generation heat management materials and electronics. Here are a few potential applications.

High-Powered Electronics

Imagine having your laptop on your lap all day without any heat dispersion. The integration of these highly conductive thermal barriers could help to drive a new era in high-tech and portable electronics. Devices could get faster and more powerful without needing additional cooling system support.

Electric Vehicles (EVs) and Power Electronics

The EV market could see significant improvements in performance due to the integration of BAs as thermal conductors. These materials could potentially enable manufacturers to make their vehicles lighter and safer. As such, they could indirectly get more mileage out of a single charge. Additionally, this strategy could reduce costs for EVs in the future.

Data Centers

Data centers will be among the first to see the benefits of this technology. These massive ecosystems are in high demand thanks to the AI market hitting record expansions. As such, this technology will have a direct impact on the AI sector in terms of its capabilities, performance, and overhead moving forward.

Boron Arsenide Timeline

Civilians could see this type of heat coating used in their electronics within the next 7-10 years. However, military and other specialty high-tech use cases might gain access to these materials in the coming 5 years or less. The fact that it costs much less to manufacture and is more readily accessible should help to reduce integration times significantly.

Boron Arsenide Researchers

The Thermal conductivity of boron arsenide above 2100 W per meter per Kelvin at room temperature study was a collaborative effort that combined research from several prestigious institutions, including the University of California, Santa Barbara,  Boston College, and the University of Houston.

Specifically, the paper lists Professor Zhifeng Ren, Bolin Liao, Ange Benise Niyikiza, Zeyu Xiang, Fanghao Zhang, Fengjiao Pan, Chunhua Li, Matthew Delmont, David Broido, and Ying Peng as contributors to the work.

Future Research Directions for BAs Materials

Given the years of work it took to achieve this monumental milestone, it’s expected that the team will continue on its journey to enhance BA’s thermal conductivity. In the future, they will also look into the use of other materials that might provide comparable or better results.

Investing in Graphite Manufacturing

There are many firms that produce thermal conductive coatings. These companies are crucial to today’s high-tech, transportation, and industrial sectors. Here’s one firm that has been pivotal in the market due to its pioneering efforts and products.

Graphjet Technology

Graphjet Technology launched in 2019. This Malaysian graphite manufacturer provides anode material and other crucial materials to today’s EV market, electronics, and communication systems.

The company has been a pioneer in the market for several reasons and has strategic partnerships with MIT, the University of Manchester, and many others seeking to expand its unique sustainable approach.

Graphjet Technology differs from its competitors in many ways. For one, the company is all about sustainability. It’s the first manufacturer in the world to create an industrial-scale process that converts agricultural waste in the form of recycled palm kernel shells into battery-grade graphite.

The company’s Malaysian facility delivers high-purity artificial graphite, single-layer graphene, and other essential materials. Impressively, the facility can convert  9,000 metric tons of waste into 3,000 metric tons of graphite annually. Additionally, it only emits  2.95 kg CO2 per kg of graphite, making it 83% cleaner than alternatives.

All of these factors continue to drive investor attention towards Graphjet Technologies. Those seeking an innovative and sustainable manufacturing stock should do more research into Graphjet shares.